Method and system for providing a magnetic read transducer having a bilayer magnetic seed layer

ABSTRACT

A method and system for providing a magnetic read transducer is described. The magnetic read transducer includes a bilayer magnetic seed layer, an antiferromagnetic (AFM) layer, and a read sensor. The bilayer magnetic seed layer includes a Ni 1-x Fe x  layer and a Ni 1-y Fe y  layer on the Ni 1-x Fe x  layer, where x is at least 0.3 and not more than 1 and where y is not more than 0.19. The AFM layer resides on the bilayer magnetic seed layer. The read sensor is on the AFM layer.

BACKGROUND

FIG. 1 depicts a portion of a conventional magnetic transducer 10, suchas a conventional read transducer, as viewed from the air-bearingsurface (ABS). The conventional transducer 10 includes a conventionalbottom shield 12, a nonmagnetic underlayer 13, conventional NiFe seedlayer 14, conventional nonmagnetic seed layer 16, conventionalantiferromagnetic (AFM) layer 18, conventional sensor 20, conventionalcapping layer 36, and conventional top shield 40. The conventionalshields 12 and 40 typically include NiFe and are formed by plating. Theconventional underlayer 13 typically includes materials such as Ta,CoFeB, and NiFeB. The conventional nonmagnetic seed layer 16 istypically Ru or NiFeCr.

The conventional sensor 20 is in a current-perpendicular to plane (CPP)configuration. In a CPP configuration, read current is driven generallyperpendicular to the plane of the layers of the device, along the z-axisshown. The sensor 20 typically includes a conventional pinned layer 24,a conventional nonmagnetic spacer layer 28, and a conventional referencelayer 30. The conventional nonmagnetic spacer layer 28 is typically atunneling barrier layer. The conventional free layer 34 has amagnetization that is substantially free to change direction in responseto an applied magnetic field, for example from a bit being read. Theconventional tunneling barrier layer 32 may allow conduction through thesensor 20 via tunneling. The sensor 20 is thus a tunnelingmagnetoresistive (TMR) sensor. Note that if a conductive spacer layer isused instead of the barrier layer 32, then the sensor 20 is a spinvalve. The pinned layer 24 shown is a synthetic antiferromagnet (SAF)includes a first pinned layer 26, a nonmagnetic spacer 28, and areference layer 30. The reference layer 30 and pinned layer 26 aretypically antiferromagnetically coupled. The magnetization(s) of theconventional SAF layer 24 are pinned by the conventional AFM layer 18.More specifically, the pinned layer 26 typically has its magnetizationpinned by the conventional AFM layer 18, for example via exchangeinteraction. The remaining ferromagnetic layer, or reference layer 30,has its magnetization pinned because it is strongly magnetically coupledwith the pinned layer 26.

The conventional transducer 10 also includes a conventional NiFe seedlayer 14. The NiFe seed layer 14 is approximately fifty percent Ni andfifty percent Fe (Ni_(0.5)Fe_(0.5)). The conventional Ni_(0.5)Fe_(0.5)seed layer 14 is magnetic. Such a conventional Ni_(0.5)Fe_(0.5) seedlayer 14 improves the thermal stability of the AFM layer 18 grown on theconventional Ni_(0.5)Fe_(0.5) seed layer 14. In particular, as therecording density increases, the distance between the shields 12 and 40is reduced. The AFM layer 18 has a decreased volume. This decrease involume may reduce the distribution of blocking temperatures (TbD). Thelowering of the TbD reduces the thermal stability of the AFM layer 18and, therefore, the stability of the SAF pinned layer 24. This wouldadversely affect performance of the conventional transducer 10. Theconventional mechanism for addressing this is the use of theNi_(0.5)Fe_(0.5) seed layer 14. If the AFM layer 18 is grown on theconventional Ni_(0.5)Fe_(0.5) seed layer 14, then the AFM layer 18 has alarger grain size, a higher anisotropic energy or both. Thus, thethermal stability of the read sensor 20 may be improved even at higherrecording densities and smaller shield-to-shield spacing.

Although the conventional sensor 20 functions, there are drawbacks. Forexample, the conventional Ni_(0.5)Fe_(0.5) seed layer 14 typically has avery large positive magnetostriction. The magnetostriction may adverselyaffect sensor 20 performance. For example, more noise may be generated.This magnetostriction may also induce an undesired magnetic anisotropyperpendicular to the ABS. The magnetic anisotropy of theNi_(0.5)Fe_(0.5) seed layer 14, which may be considered to be part ofthe shield 12, affects the shield 12. The conventional shield 12 maythus become unstable during recording or in the presence of externalstray fields. In addition, the conventional Ni_(0.5)Fe_(0.5) seed layer14 may be overmilled at its sides. If this occurs, the relatively highmagnetization of the conventional Ni_(0.5)Fe_(0.5) seed layer 14 mayweaken the effect of hard bias layer (not shown). As a result, the freelayer response amplitude, asymmetry, and noise are adversely affected.Thus, the conventional read transducer 10 may not function as desired athigher recording densities.

Accordingly, what is needed is a system and method for providing a readtransducer having improved performance at higher densities.

BRIEF SUMMARY OF THE INVENTION

A method and system for providing a magnetic read transducer isdescribed. The magnetic read transducer includes a bilayer magnetic seedlayer, an antiferromagnetic (AFM) layer, and a read sensor. The bilayermagnetic seed layer includes a Ni_(1-x)Fe_(x) layer and a Ni_(1-y)Fe_(y)layer on the Ni_(1-x)Fe_(x) layer, where x is at least 0.3 and not morethan 1 and where y is not more than 0.19. The AFM layer resides on thebilayer magnetic seed layer. The read sensor is on the AFM layer.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram depicting an ABS view of a portion of a conventionaltransducer including a conventional sensor.

FIG. 2 depicts an exemplary embodiment of a head including an exemplaryembodiment of a transducer.

FIG. 3 depicts an ABS view of a portion of an exemplary embodiment of aread transducer.

FIG. 4 depicts an ABS view of a portion of another exemplary embodimentof a read transducer.

FIG. 5 depicts an ABS view of a portion of another exemplary embodimentof a read transducer.

FIG. 6 depicts an exemplary embodiment of a method of forming anexemplary embodiment of a read transducer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 depicts a magnetic head 100. FIG. 2 is not to scale and not allcomponents of the magnetic head 100 are shown. The magnetic head 100 isa merged head that includes a magnetic write transducer 110 and amagnetic read transducer 150. In other embodiments, the read transducer150 and write transducer 110 may also be in separate heads. The magnetichead 100 resides on a slider and is typically one of many magnetic headsin a disk drive and used to write to and read from a media (not shown).The write transducer 110 includes a first pole 112, auxiliary pole 116,main pole 118, write gap 120, coils 114 and 122, and return shield 124.However, in another embodiment, the write transducer 110 includes otherand/or different components. In addition, one or more portions of thewrite transducer 110 might be omitted in various embodiments.

The read transducer 150 includes shields 152 and 154, bilayer magneticseed layer 160, pinning layer 170, and sensor 180. The sensor 180 may beused to read data from a media (not shown). The shields 152 and 154 maybe a soft magnetic material, such as NiFe. The shields 152 and 154magnetically isolate the sensor 180 from bits not being read duringoperation of the transducer 150. The sensor 180 resides on the pinninglayer 170.

The pinning layer 170 may be used to fix, or pin, the magnetization of alayer in the sensor 180, such as a pinned layer (not shown in FIG. 2).The pinning layer 170 may be an AFM layer. The pinning layer 170 is onthe bilayer magnetic seed layer 160. In some embodiments, a nonmagneticseed layer (not shown) resides between the bilayer magnetic seed layer160 and the pinning layer 170.

The bilayer magnetic seed layer 160 includes a Ni_(1-x)Fe_(x) layer anda Ni_(1-y)Fe_(y) layer on the Ni_(1-x)Fe_(x) layer, where x is at least0.3 and not more than 1 and where y is not more than 0.19. In someembodiments, x is at least 0.45 and not more than 0.55. In someembodiments, y is at least 0.05 and not more than 0.15. TheNi_(1-x)Fe_(x) layer is between the Ni_(1-y)Fe_(y) layer and the shield152. Although described in terms of two separate layers, in someembodiments, the bilayer magnetic seed layer 160 may not containseparate layers. Instead, the Ni_(1-x)Fe_(x) layer and theNi_(1-y)Fe_(y) layer may be formed by a gradient in concentrationbetween the edge closest to the shield 152 and the edge of the bilayermagnetic seed layer 160 closest to the pinning layer 170. However, inother embodiments, there is a sharp interface between the Ni_(1-x)Fe_(x)layer and the Ni_(1-y)Fe_(y) layer. In addition, the bilayer magneticseed 160 includes at least two NiFe layers having the concentrationsdescribed above. In some embodiments, the bilayer magnetic seed layer160 may include additional layer(s) having intermediate concentrations.In some embodiments, the Ni_(1-x)Fe_(x) layer has a thickness of atleast ten Angstroms and not more than five hundred Angstroms.

Use of the bilayer magnetic seed layer 160 may improve performance ofthe transducer 150 and thus the head 100. The Ni_(1-x)Fe_(x) layer has ahigher concentration of Fe. The higher concentration of Fe results in ahigher TbD and increases the coercivity of a pinned layer (not shown) inthe sensor 160. As a result, the stability of the sensor 160 may beimproved. The Ni_(1-y)Fe_(y) layer has a lower concentration of Fe. TheNi_(1-y)Fe_(y) layer thus has a lower magnetic moment than theNi_(1-x)Fe_(x) layer. As a result, issues due to a high moment of themagnetic seed layer 160 such as issues due to overmilling may bereduced. In addition, the Ni_(1-y)Fe_(y) layer may have magnetostrictionopposite to that of the Ni_(1-x)Fe_(x) layer. For example, theNi_(1-y)Fe_(y) layer may have negative magnetostriction, while theNi_(1-x)Fe_(x) layer has a positive magnetostriction. The totalmagnetostriction of the bilayer magnetic seed layer 160 may thus bereduced or brought to zero by balancing the magnetostrictions. Thus, thebilayer magnetic seed layer 160 may be less likely to induce unwantedanisotropies, improving the stability of the shield 152.

FIG. 3 depicts an exemplary embodiment of the read transducer 150 asused in the magnetic recording head 100. For clarity, FIG. 3 is not toscale. The transducer 150 is also described in the context of particularlayers. However, in some embodiments, such layers may includesub-layer(s). The read transducer 150 is shown in a CPP configuration.Thus, sensor 180 is electrically connected to the shields 152 and 154.However, in another embodiment, a gap may exist between the sensor 180and the shields 152 and/or 154. Further, a configuration other than CPPmight be used. The read transducer 150 is also described in the contextof particular layers. However, in some embodiments, such layers mayinclude sub-layer(s).

The read transducer 150 includes shields 152 and 154, bilayer magneticseed layer 160, pinning layer 170, and sensor 180 analogous to thosedepicted in FIG. 2. The pinning layer 170 may be an AFM layer. Forexample, the pinning layer 170 may be an IrMn layer. The pinning layer170 is on the bilayer magnetic seed layer 160. In some embodiments, anonmagnetic seed layer (not shown) resides between the bilayer magneticseed layer 160 and the pinning layer 170. For example, such anonmagnetic seed layer may include at least one of Ru, NiFeZ, and NiZ,where Z is at least one of Cr, Zr, Rh, and Ta.

The bilayer magnetic seed layer 160 includes a Ni_(1-x)Fe_(x) layer(labeled NiFe seed layer 1 in FIG. 3) 162 and a Ni_(1-y)Fe_(y) layer 164(labeled NiFe seed layer 2 in FIG. 3) on the Ni_(1-x)Fe_(x) layer 162,where x is at least 0.3 and not more than 1 and where y is not more than0.19. In some embodiments, x is at least 0.45 and not more than 0.55. Insome embodiments, y is at least 0.05 and not more than 0.15. TheNi_(1-x)Fe_(x) layer 162 is thus between the Ni_(1-y)Fe_(y) layer 164and the shield 152. In some embodiments, the Ni_(1-x)Fe_(x) layer 162has a thickness of at least ten Angstroms and not more than one hundredAngstroms. In some such embodiments, the thickness of the Ni_(1-x)Fe_(x)162 layer is at least fifteen Angstroms and not more than fiftyAngstroms. In some embodiments, the Ni_(1-y)Fe_(y) layer 164 has athickness of at least ten Angstroms and not more than five hundredAngstroms. In some embodiments, the layers 162 and 164 are formed bychanging the concentration of Ni and Fe throughout the layer 160. Insome embodiments, the bilayer magnetic seed layer 160 is grown onanother magnetic seed layer (not shown in FIG. 3).

The transducer depicted in FIG. 3 shares the benefits of the transducer150 depicted in FIG. 2. The combination of the layers 162 and 164 in thebilayer magnetic seed layer 160 may result in improved thermal stabilityof the sensor 180. More specifically, the desired structure of thepinning layer 170 may be achieved for lower volumes of the pinning layer170 and lower shield-too-shield spacing. Issues due to magnetostrictionof the bilayer magnetic seed layer 160 may also be reduced oreliminated. As a result, the stability of the sensor 160 and shield 152may be improved. Consequently, performance of the magnetic transducer150 may be improved.

FIG. 4 depicts another exemplary embodiment of a read transducer 150′including a bilayer magnetic seed layer 160′. For clarity, FIG. 4 is notto scale. The transducer 150′ is also described in the context ofparticular layers. However, in some embodiments, such layers may includesub-layer(s). The read transducer 150′ is shown in a CPP configuration.Thus, sensor 180′ is electrically connected to the shields 152′ and154′. However, in another embodiment, a gap may exist between the sensor180′ and the shields 152′ and/or 154′. A configuration other than CPPmay also be used. The read transducer 150′ is also described in thecontext of particular layers. However, in some embodiments, such layersmay include sub-layer(s).

Portions of the transducer 150′ are analogous to those of the head 100and transducer 150 shown in FIGS. 2-3. Such analogous structures arelabeled similarly. The transducer 150′ thus includes shields 152′ and154′, bilayer magnetic seed layer 160′, pinning layer 170′, and sensor180′ that are analogous to the shields 152 and 154, bilayer magneticseed layer 160, pinning layer 170, and sensor 180, respectively.However, the pinning layer 170′ is expressly indicated to be an AFMlayer 170′. For example, the AFM layer 170′ may be an IrMn or otheranalogous layer. In the embodiment shown, the AFM layer 170′ is grown onthe bilayer magnetic seed layer 160′. However, in other embodiments, anadditional seed layer may be used between the layers 160′ and 170′.

The sensor 180′ includes a pinned layer 181, a nonmagnetic layer 188, afree layer 190, and an optional capping layer 192. The capping layer 192is nonmagnetic and may include materials such as Ta. The pinned layer181 shown is a SAF including ferromagnetic pinned layer 182, nonmagneticspacer layer 184, and ferromagnetic reference layer 186. The pinnedlayer 182 has its magnetization fixed, or pinned, by the AFM layer 170′.The reference layer 186 is magnetically coupled to the pinned layer 182and has its magnetization fixed through this interaction. In otherembodiments, the pinned layer 181 may have another structure, such as asingle layer or a multilayer. The free layer 190 includes one or moreferromagnetic layers (not separately shown in FIG. 4) and is the sensorlayer for the sensor 180′. In some embodiments, the free layer 190 mayalso include nonmagnetic layers. The nonmagnetic layer 188 separates thefree layer 190 from the pinned layer 181. The nonmagnetic layer 188 mayalso be desired to support a large magnetoresistance for the sensor180′. In some embodiments, the nonmagnetic layer 188 is an insulating,tunneling barrier layer, such as crystalline MgO. In other embodiments,the nonmagnetic layer 188 may be conductive and/or have anotherstructure.

The bilayer magnetic seed layer 160′ includes a Ni_(1-x)Fe_(x) layer(labeled NiFe seed layer 1 in FIG. 4) 162′ and a Ni_(1-y)Fe_(y) layer164′ (labeled NiFe seed layer 2 in FIG. 4) on the Ni_(1-x)Fe_(x) layer162′, where x is at least 0.3 and not more than 1 and where y is notmore than 0.19. In some embodiments, x is at least 0.45 and not morethan 0.55. In some embodiments, y is at least 0.05 and not more than0.15. The Ni_(1-x)Fe_(x) layer 162′ is between the Ni_(1-y)Fe_(y) layer164′ and the shield 152′. In some embodiments, the Ni_(1-x)Fe_(x) layer162′ has a thickness of at least ten Angstroms and not more than onehundred Angstroms. In some such embodiments, the thickness of theNi_(1-x)Fe_(x) 162′ layer is at least fifteen Angstroms and not morethan fifty Angstroms. In some embodiments, the Ni_(1-y)Fe_(y) layer 164′has a thickness of at least ten Angstroms and not more than five hundredAngstroms. In some embodiments, the layers 162′ and 164′ are formed bychanging the concentration of Ni and Fe throughout the layer 160′. Insome embodiments, the bilayer magnetic seed layer 160′ is grown onanother magnetic seed layer (not shown in FIG. 4).

The transducer 150′ depicted in FIG. 4 shares the benefits of thetransducer 150 depicted in FIGS. 2-3. The combination of the layers 162′and 164′ in the bilayer magnetic seed layer 160′ may result in improvedthermal stability of the sensor 180′. More specifically, the desiredstructure of the pinning layer 170′ may be achieved for lowershield-too-shield spacing. Issues due to magnetostriction of the bilayermagnetic seed layer 160′ may also be reduced or eliminated. As a result,the stability of the sensor 160′ and shield 152′ may be improved.Consequently, performance of the magnetic transducer 150′ may beimproved.

FIG. 5 depicts an ABS view of another exemplary embodiment of a readtransducer 150″ including a bilayer magnetic seed layer 160″. Forclarity, FIG. 5 is not to scale. The transducer 150″ is also describedin the context of particular layers. However, in some embodiments, suchlayers may include sub-layer(s). The read transducer 150″ is shown in aCPP configuration. Thus, sensor 180′ is electrically connected to theshields 152″ and 154″. However, in another embodiment, a gap may existbetween the sensor 180″ and the shields 152″ and/or 154″. Aconfiguration other than CPP may also be used. The read transducer 150″is also described in the context of particular layers. However, in someembodiments, such layers may include sub-layer(s).

Portions of the transducer 150″ are analogous to those of the head 100and transducers 150/150′ shown in FIGS. 2-4. Such analogous structuresare labeled similarly. The transducer 150″ thus includes shields 152″and 154″, bilayer magnetic seed layer 160″, pinning layer 170″, andsensor 180″ that are analogous to the shields 152/152′ and 154/154′,bilayer magnetic seed layer 160/150′, pinning layer 170/170′, and sensor180/180′, respectively. The pinning layer 170″ is expressly indicated tobe an AFM layer 170″. For example, the AFM layer 170″ may be an IrMn orother analogous layer. The sensor 180″ includes a pinned layer 181′having layers 182′, 184′, and 186′, a nonmagnetic layer 188′, a freelayer 190′, and an optional capping layer 192′ analogous to the pinnedlayer 181 having layers 182, 184, and 186, the nonmagnetic layer 188,the free layer 190, and the optional capping layer 192, respectively.

The bilayer magnetic seed layer 160″ includes a Ni_(1-x)Fe_(x) layer(labeled NiFe seed layer 1 in FIG. 5) 162″ and a Ni_(1-y)Fe_(y) layer164″ (labeled NiFe seed layer 2 in FIG. 5) on the Ni_(1-x)Fe_(x) layer162″, where x is at least 0.3 and not more than 1 and where y is notmore than 0.19. In some embodiments, x is at least 0.45 and not morethan 0.55. In some embodiments, y is at least 0.05 and not more than0.15. The Ni_(1-x)Fe_(x) layer 162″ is between the Ni_(1-y)Fe_(y) layer164′ and the shield 152″. The structure, geometry, and function of theNi_(1-x)Fe_(x) layer 162″ and the Ni_(1-y)Fe_(y) layer 164″ areanalogous to that of the Ni_(1-x)Fe_(x) layer 162/162′ and theNi_(1-y)Fe_(y) layer 164/164′.

In addition, the transducer 150″ includes optional interlayer 192. Forexample, the interlayer 192 may be CoFeB and/or NiFeB. In someembodiments, the interlayer 192 is magnetic. In other embodiments,however, the interlayer 192 is nonmagnetic. The transducer 150″ alsoincludes optional nonmagnetic seed layer 194. The nonmagnetic seed layer194 may include material such as Ru, and NiZ, where Z is at least one ofCr, Zr, Rh, and Ta. In some embodiments, the nonmagnetic seed layer 194may be used to break or reduce the magnetic coupling between the bilayermagnetic seed layer 160″ and the AFM layer 170″.

The transducer 150″ depicted in FIG. 5 shares the benefits of thetransducers 150/150′/150″ depicted in FIGS. 2-4. The combination of thelayers 162″ and 164″ in the bilayer magnetic seed layer 160″ may resultin improved thermal stability of the sensor 180″. More specifically, thedesired structure of the pinning layer 170″ may be achieved for lowershield-too-shield spacing. Issues due to magnetostriction of the bilayermagnetic seed layer 160′ may also be reduced or eliminated. As a result,the stability of the sensor 160″ and shield 152″ may be improved.Consequently, performance of the magnetic transducer 150″ may beimproved.

FIG. 6 depicts an exemplary embodiment of a method 200 of forming anexemplary embodiment of a read transducer including a bilayer magneticseed layer. For simplicity, some steps may be omitted, combined, and/orinterleaved. The method 200 is described in the context of thetransducer 150″. However, the method 200 may be used for othertransducers. The method 200 also may commence after formation of otherstructures of the read and/or write transducer. The method 200 is alsodescribed in the context of providing a single transducer 150″. However,the method 200 may be used to fabricate multiple structures atsubstantially the same time. The method 200 and structures such as thetransducers 150/150′/150″/150′″ are also described in the context ofparticular layers. However, in some embodiments, such layers may includesub-layer(s).

The first shield 152″ is provided, via step 202. In some embodiments,the first shield 152″ is plated on the substrate 151″. However, in otherembodiments, first shield 152″ is deposited in another manner and/or onanother structure. The interlayer 192 may optionally be provided on thefirst shield, via step 204. The bilayer magnetic seed layer 160″ isdeposited in step 206. In some embodiments, step 206 includes depositingtwo separate layers 162″ and 164″. In other embodiments, the layer 162″and 164″ are provided by changing the concentration of the Ni and Feacross the bilayer magnetic seed layer 160″. The nonmagnetic seed layer194 may optionally be provided, via step 208. The AFM pinning layer 170″and read sensor 180″ are provided via steps 210 and 212, respectively.In some embodiments, steps 210 and 212 include depositing the layers170″, 182′, 184′, 186′, 188′, 190′, and 192′, and then defining the AFM170″ and read sensor 180″ in the track width and stripe height(perpendicular to the ABS) directions. Fabrication of the transducer150″ may then be completed, via step 214. For example, hard bias orother analogous structures may be provided. The top shield 154″ may alsobe provided.

Using the method 200 fabrication of the transducers 150, 150′, and/or150″, as well as head 100 may be completed. Thus, the benefits of thetransducers 150, 150′, and/or 150″ may be achieved.

We claim:
 1. A magnetic read transducer comprising: a bilayer magneticseed layer including a Ni_(1-x)Fe_(x) layer and a Ni_(1-y)Fe_(y) layeron and sharing an interface with the Ni_(1-x)Fe_(x) layer, where x is atleast 0.3 and not more than 1 and where y is not more than 0.19; anantiferromagnetic (AFM) layer residing on the bilayer magnetic seedlayer; a read sensor on the AFM layer.
 2. The magnetic read transducerof claim 1 further comprising: a nonmagnetic seed layer on the bilayermagnetic seed layer, the AFM layer residing on the nonmagnetic seedlayer.
 3. The magnetic read transducer of claim 2 wherein thenonmagnetic seed layer includes at least one of Ru, NiFeZ, and NiZ,where Z is at least one of Cr, Zr, Rh, and Ta.
 4. The magnetic readtransducer of claim 1 wherein x is at least 0.45 and not more than 0.55.5. The magnetic read transducer of claim 1 wherein y is at least 0.05and not more than 0.15.
 6. The magnetic read transducer of claim 1wherein the Ni_(1-x)Fe_(x) layer has a thickness of at least tenAngstroms and not more than one hundred Angstroms.
 7. The magnetic readtransducer of claim 6 wherein the thickness is at least fifteenAngstroms and not more than fifty Angstroms.
 8. The magnetic readtransducer of claim 1 wherein the Ni_(1-y)Fe_(y) layer has a thicknessof at least ten Angstroms and not more than five hundred Angstroms. 9.The magnetic read transducer of claim 8 wherein the thickness is atleast fifty Angstroms and not more than two hundred.
 10. The magneticread transducer of claim 1 wherein the read sensor includes a pinnedlayer on the AFM layer, a free layer, and a nonmagnetic spacer layerbetween the pinned layer and the free layer.
 11. The magnetic readtransducer of claim 10 further comprising a first shield and a secondshield, the bilayer magnetic seed layer, the AFM layer, and the readsensor residing between the first shield and the second shield.
 12. Themagnetic read transducer of claim 11 further comprising: an interlayerbetween the first shield and the bilayer magnetic seed layer, theinterlayer including at least one of CoFeB and NiFeB.
 13. A magneticread transducer comprising: a first shield; an interlayer including atleast one of CoFeB and NiFeB on the first shield; a bilayer magneticseed layer on the interlayer, the bilayer magnetic seed layer includinga Ni_(1-x)Fe_(x) layer having a first thickness and a Ni_(1-y)Fe_(y)layer on the Ni_(1-x)Fe_(x) layer, the Ni_(1-y)Fe_(y) sharing aninterface with the Ni_(1-x)Fe_(x) layer, the Ni_(1-y)Fe_(y) layer havinga second thickness, where x is at least 0.45 and not more than 0.55 andwhere y is at least 0.05 and not more than 0.15, the first thicknessbeing fifteen Angstroms and not more fifty Angstroms, the secondthickness being at least fifty Angstroms and not more than two hundredAngstroms; a nonmagnetic seed layer on the bilayer magnetic seed layer,the nonmagnetic seed layer including at least one of Ru, NiFeZ, and NiZ,where Z is at least one of Cr, Zr, Rh, and Ta; an antiferromagnetic(AFM) layer residing on the nonmagnetic seed layer; a read sensor on theAFM layer, the read sensor including a pinned layer on the AFM layer, afree layer, and a nonmagnetic spacer layer between the pinned layer andthe free layer, the pinned layer being a synthetic antiferromagneticlayer including a first magnetic layer, a second magnetic layer, and anonmagnetic layer between the first magnetic layer and the secondmagnetic layer, the nonmagnetic spacer layer being a tunneling barrierlayer; a capping layer on the read sensor; and a second shield on thecapping layer.